Air conditioning systems that reside outside a commercial building or residence, such as refrigeration units and heat pumps, are well known. In some applications, these outside units must operate in both warm and cold climate conditions. One such example is a heat pump. A heat pump may be reversibly configured to heat or to cool a climate-controlled space. This dual-role capability may allow the heat pump to replace a separate air conditioner/furnace combination. However, because the heat pump uses electricity for both heating and cooling, efficiency (e.g. HSPF) is of utmost importance. When the unit receives an “on command” from a primary controller, such as a thermostat, located in the commercial building or residence, a motor with fan blades attached thereto is turned on to produce an air flow through the exterior unit.
Under some operating conditions, ice may form between the fan blades and a housing component, thereby blocking fan blade and preventing the fan blade from turning when an “on command” is received. Alternatively, the weight of snow build up on the fan blades may be sufficient to prevent the fan blades from turning. Yet in other instances, a foreign object, such as a tree limb, can become lodge between the fan blades and the housing to prevent fan blade rotation.
In such instances in conventional units, if the motor senses a resistance to the rotation of the fan blades due to one or more of the aforementioned obstacles, the motor will automatically shut down to prevent damage to the motor. When this occurs, the unit is unable to operate normally until the blocking obstacle is removed to free the fan blade. This may require servicing the unit to remove the obstacle, which can be time consuming, costly, and can cause an extended disruption of service.